On Sat, 27 Aug 2011 17:52:02 +0800, Wang Sheng-Hui <shhuiw@xxxxxxxxx> wrote:
> On 2011年08月27日 17:34, Wang Sheng-Hui wrote:
> diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
> index 4a32cb6..300af76 100644
> --- a/include/linux/virtio_ring.h
> +++ b/include/linux/virtio_ring.h
> @@ -135,13 +135,13 @@ static inline void vring_init(struct vring *vr, unsigned int num, void *p,
> vr->num = num;
> vr->desc = p;
> vr->avail = p + num*sizeof(struct vring_desc);
> - vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + align-1)
> - & ~(align - 1));
> + vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + 16
> + + align-1) & ~(align - 1));
> }
This + 16 should be + sizeof(__u16), right? It's just the
used_event_idx which has been added:
* __u16 available[num];
* __u16 used_event_idx;
*
* // Padding to the next align boundary.
* char pad[];
*
* [USED]
> static inline unsigned vring_size(unsigned int num, unsigned long align)
> {
> - return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
> + return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (3 + num)
> + align - 1) & ~(align - 1))
> + sizeof(__u16) * 3 + sizeof(struct vring_used_elem) * num;
This is correct.
And, yes, since align is always 4096, it's currently just a cleanup, but
it makes things much less confusing!
Thanks,
Rusty.
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